Inhibition of the proteasome activity by graphene oxide contributes to its cytotoxicity

The Synergistic Effect of Reduced Graphene Oxide and Proteasome Inhibitor in the Induction of Apoptosis through Oxidative Stress in Breast Cancer Cell Lines

Reduced graphene oxide (rGO) and a proteasome inhibitor (MG-132) are some of the most commonly used compounds in various biomedical applications. However, the mechanisms of rGO- and MG-132-induced cytotoxicity remain unclear. The aim of this study was to investigate the anticancer effect of rGO and MG-132 against ZR-75-1 and MDA-MB-231 breast cancer cell lines. The results demonstrated that rGO, MG-132 or a mix (rGO + MG-132) induced time- and dose-dependent cytotoxicity in ZR-75-1 and MDA-MB-231 cells. Apart from that, we found that treatment with rGO and MG-132 or the mix increased apoptosis, necrosis and induction of caspase-8 and caspase-9 activity in both breast cancer cell lines. Apoptosis and caspase activation were accompanied by changes in the ultrastructure of mitochondria in ZR-75-1 and MDA-MB-231 cells incubated with rGO. Additionally, in the analyzed cells, we observed the induction of oxidative stress, accompanied by increased apoptosis and cell necrosis. In conclusion, oxidative stress induces apoptosis in the tested cells. At the same time, both mitochondrial and receptor apoptosis pathways are activated. These studies provided new information on the molecular mechanisms of apoptosis in the ZR-75-1 and MDA-MB-231 breast cancer cell lines.

Gold Nanorods Inhibit Tumor Metastasis by Regulating MMP-9 Activity: Implications for Radiotherapy

Dysregulation of matrix metalloproteinase (MMP) is strongly implicated in tumor invasion and metastasis. Nanomaterials can interact with proteins and have impacts on protein activity, which provides a potential strategy for inhibiting tumor invasion and metastasis. However, the regulation of MMP activity by nanomaterials has not been fully determined. Herein, we have found that gold nanorods (Au NRs) are able to induce the change of the secondary structure of MMP-9 and thereby inhibit their activity. Interestingly, the inhibition of MMP-9 activity is highly dependent on the aspect ratio of Au NRs, and an aspect ratio of 3.3 shows the maximum inhibition efficiency. Molecular dynamics simulations combined with mathematical statistics algorithm reveal the binding behaviors and interaction modes of MMP-9 with Au NRs in atomic details and disclose the mechanism of aspect ratio-dependent inhibition effect of Au NRs on MMP-9 activity. Au NRs with an aspect ratio of 3.3 successfully suppress the X-ray-activated invasion and metastasis of tumor by inhibiting MMP-9 activity. Our findings provide important guidance for the modulation of MMP-9 activity by tuning key parameters of nanomaterials and demonstrate that gold nanorods could be developed as potential MMP inhibitors.

Molecular Insight into AC Electric Field Enhanced Removal of Protein Aggregates from a Material Surface

Biofouling, caused by unwanted accumulation of the biological molecules on the material surface, is a common problem when medical devices are planted in the human body. Application of an electric field was first suggested in the 1960s along with many other approaches to deactivate the biofouling process. There are experiments showing a higher efficiency in reducing the biofouling using the alternating current (AC) compared to the direct current (DC). Here, using molecular dynamics (MD) simulations, we compared the binding stability of a single protein molecule on a graphene surface with either an AC or a DC field was applied. We first showed that the protein molecule, initially attached to the graphene surface, will spontaneously be desorbed by the applied AC electric field, while it remains intact under the DC field of the same voltage. We then revealed that the desorption of the protein by the AC electric field is kinetically controlled. As the orientation of the protein changed alongside the reversing electric field, the protein-graphene interface would be destabilized the most if the AC frequency was close to that of the relaxation of the protein dipole moment (i.e., resonance).

Influence of zinc doping on the molecular biocompatibility of cadmium-based quantum dots: Insights from the interaction with trypsin

Doping quantum dots (QDs) with extra element presents a promising future for their applications in the fields of environmental monitoring, commercial products and biomedical sciences. However, it remains unknown for the influence of doping on the molecular biocompatibility of QDs and the underlying mechanisms of the interaction between doped-QDs and protein molecules. Using the "one-pot" method, we synthesized N-acetyl-l-cysteine capped CdTe: Zn²⁺ QDs with higher fluorescence quantum yield, improved stability and better molecular biocompatibility compared with undoped CdTe QDs. Using digestive enzyme trypsin (TRY) as the protein model, the interactions of undoped QDs and Zn-doped QDs with TRY as well as the underlying mechanisms were investigated using multi-spectroscopy, isothermal titration calorimetry and dialysis techniques. Van der Waals forces and hydrogen bonds are the major driving forces in the interaction of both QDs with TRY, which leading to the loosening of protein skeleton and tertiary structural changes. Compared with undoped QDs, Zn-doped QDs bind less amount of TRY with a higher affinity and then release higher amount of Cd. Zn-doped QDs have a less stimulating impact on TRY activity by decreasing TRY binding and reducing Cd binding to TRY. Taken all together, Zn-doped QDs offer a safer alternative for the applications of QDs by reducing unwanted interactions with proteins and improving biocompatibility at the molecular level.

Biomedical application of chitosan-based nanoscale delivery systems: Potential usefulness in siRNA delivery for cancer therapy

Gene therapy is an emerging and promising strategy in cancer therapy where small interfering RNA (siRNA) system has been deployed for down-regulation of targeted gene and subsequent inhibition in cancer progression; some issues with siRNA, however, linger namely, its off-targeting property and degradation by enzymes. Nanoparticles can be applied for the encapsulation of siRNA thus enhancing its efficacy in gene silencing where chitosan (CS), a linear alkaline polysaccharide derived from chitin, with superb properties such as biodegradability, biocompatibility, stability and solubility, can play a vital role. Herein, the potential of CS nanoparticles has been discussed for the delivery of siRNA in cancer therapy; proliferation, metastasis and chemoresistance are suppressed by siRNA-loaded CS nanoparticles, especially the usage of pH-sensitive CS nanoparticles. CS nanoparticles can provide a platform for the co-delivery of siRNA and anti-tumor agents with their enhanced stability via chemical modifications. As pre-clinical experiments are in agreement with potential of CS-based nanoparticles for siRNA delivery, and these carriers possess biocompatibiliy and are safe, further studies can focus on evaluating their utilization in cancer patients.

Matrix metalloproteinase inhibitors (MMPIs) as attractive therapeutic targets: Recent progress and current challenges

Matrix metalloproteinase (MMP) plays an essential role in many physiological and pathological processes. An increase in MMP activity contributes to excessive degradation and remodeling of the extracellular matrix (ECM), which has been correlated with invasion and metastasis of tumors. Matrix metalloproteinase inhibitor (MMPI) has been developed as an attractive therapeutic target for decades, suggesting inspiring therapeutic effects in preclinical studies. However, achieving specificity remains an important challenge in the development of MMPIs, limiting their clinical application and bringing about the risk of biosafety. Nanomaterials can be used as alternative candidates for MMPI design, providing a new strategy for this problem. This report reviewed the research about MMPIs, summarized their MMPs activity regulation mechanisms, and discussed their failures in clinical trials. Furthermore, we outlined several schemes of MMPIs screening and design. Finally, we reviewed the therapeutic application prospects of MMPIs and discussed the remaining challenges and solutions, which may offer new insights for the development of MMPIs studies.

Codelivery of HIF-1α siRNA and Dinaciclib by Carboxylated Graphene Oxide-Trimethyl Chitosan-Hyaluronate Nanoparticles Significantly Suppresses Cancer Cell Progression

PURPOSE

Hypoxia-inducible factor (HIF) is one of the critical components of the tumor microenvironment that is involved in tumor development. HIF-1α functionally and physically interacts with CDK1, 2, and 5 and stimulates the cell cycle progression and Cyclin-Dependent Kinase (CDK) expression. Therefore, hypoxic tumor microenvironment and CDK overexpression lead to increased cell cycle progression and tumor expansion. Therefore, we decided to suppress cancer cell expansion by blocking HIF-1α and CDK molecules.

METHODS

In the present study, we used the carboxylated graphene oxide (CGO) conjugated with trimethyl chitosan (TMC) and hyaluronate (HA) nanoparticles (NPs) loaded with HIF-1α-siRNA and Dinaciclib, the CDK inhibitor, for silencing HIF-1α and blockade of CDKs in CD44-expressing cancer cells and evaluated the impact of combination therapy on proliferation, metastasis, apoptosis, and tumor growth.

RESULTS

The results indicated that the manufactured NPs had conceivable physicochemical properties, high cellular uptake, and low toxicity. Moreover, combination therapy of cancer cells using CGO-TMC-HA NPs loaded with HIF-1α siRNA and Dinaciclib (SCH 727965) significantly suppressed the CDKs/HIF-1α and consequently, decreased the proliferation, migration, angiogenesis, and colony formation in tumor cells.

CONCLUSIONS

These results indicate the ability of CGO-TMC-HA NPs for dual drug/gene delivery in cancer treatment. Furthermore, the simultaneous inhibition of CDKs/HIF-1α can be considered as a novel anti-cancer treatment strategy; however, further research is needed to confirm this treatment in vivo. Graphical Abstract The suppression of HIF-1α and CDKs inhibits cancer growth. HIF-1α is overexpressed by the cells present in the tumor microenvironment. The hypoxic environment elevates mitochondrial ROS production and increases p38 MAP kinase, JAK/STAT, ERK, JNK, and Akt/PI3K signaling, resulting in cyclin accumulation and aberrant cell cycle progression. Furthermore, the overexpression of HIF-1α/CDK results in increased expression of genes such as BCL2, Bcl-xl, Ki-67, TGFβ, VEGF, FGF, MMP2, MMP9, and, HIF-1α and consequently raise the survival, proliferation, angiogenesis, metastasis, and invasion of tumor cells. In conclusion, HIF-1α-siRNA/Dinaciclib-loaded CGO-TMC-HA NPs can inhibit the tumor expansion by blockage of CDKs and HIF-1α (JAK: Janus kinase, STAT: Signal transducer and activator of transcription, MAPK: mitogen-activated protein kinase, ERK: extracellular signal-regulated kinase, JNK: c-Jun N-terminal kinase, PI3K: phosphatidylinositol 3-kinase).

Investigations of conformational structure and enzymatic activity of trypsin after its binding interaction with graphene oxide

Herein, interaction between graphene oxide (GO) and trypsin was systematically characterized for deep investigations of conformational structure and enzymatic activity of trypsin affected by GO. Results indicated that GO bound with trypsin to form ground state complex with molar ratio of 1 to 1. Intrinsic fluorescence of trypsin was statically quenched by GO through van der Waal interaction, hydrophobic interaction, hydrogen bond, and electrostatic interaction. Both tertiary structure and secondary structure of trypsin were changed obviously after its binding with trypsin, resulting in the structure transformation of trypsin from the β-sheet structure to the α-helix structure. Since GO bound with the allosteric site of trypsin to inhibit its enzymatic activity via non-competitive manner, GO efficiently protected human serum albumin and human cervical carcinoma HeLa cells from the digestion of trypsin. These results explored the exact binding mechanism of GO with protease, which provides more important information for possible biological risk of GO on human beings.

Autophagy and Ubiquitin-Proteasome System Coordinate to Regulate the Protein Quality Control of Neurodegenerative Disease-Associated DCTN1

Motor neuron diseases are neurodegenerative diseases that are characterized by degeneration of the upper and lower motor neurons in the central nervous system. Mutations in Dynactin 1 (DCTN1), a component in the Dynein/Dynactin motor complex, have been previously identified to cause motor neuron diseases and other neurodegenerative disorders. Recent studies showed that motor neuron disease-linked mutation, such as G59S mutation, could lead to dysfunction and protein aggregation of DCTN1. However, the cellular pathway involved in the clearance of DCTN1 aggregates is still not fully elucidated. In this study, we employed a culture cell model of DCTN1-linked neurodegeneration and explored the role of cellular protein control systems in the regulation of wild type and mutant DCTN1. We find that the ubiquitin-proteasome system, but not autophagy, is the primary protein degradation system for the turnover of both wild type and G59S DCTN1 under normal conditions. However, it turns out that autophagy can play a role in the clearance of protein aggregates of G59S DCTN1 when the proteasome activity is inhibited. Importantly, overexpression of TFEB, a master regulator of autophagy, promotes the autophagic clearance of G59S DCTN1 aggregates and ameliorates G59S DCTN1-induced cytotoxicity when the proteasomes are impaired. In conclusion, autophagy may play as a backup system to protect cells against the cytotoxicity induced by aggregate-prone DCTN1 when proteasomal function is damaged.

Toxic effects and involved molecular pathways of nanoparticles on cells and subcellular organelles

Owing to the increasing application of engineered nanoparticles (NPs), besides the workplace, human beings are also exposed to NPs from nanoproducts through the skin, respiratory tract, digestive tract and vein injection. This review states pathways of cellular uptake, subcellular distribution and excretion of NPs. The uptake pathways commonly include phagocytosis, micropinocytosis, clathrin- and caveolae-mediated endocytosis, scavenger receptor-related pathway, clathrin- or caveolae-independent pathway, and direct penetration or insertion. Then the ability of NPs to decrease cell viability and metabolic activity, change cell morphology, and destroy cell membrane, cytoskeleton and cell function was presented. In addition, the lowest dose decreasing cell metabolic viability compared with the control or IC₅₀ of silver, titanium dioxide, zinc oxide, carbon black, carbon nanotubes, silica, silicon NPs and cadmium telluride quantum dots to some cell lines was gathered. Next, this review attempts to increase our understanding of NP-caused adverse effects on organelles, which have implications in mitochondrial dysfunction, endoplasmic reticulum stress and lysosomal rupture. In particular, the disturbance of mitochondrial biogenesis and mitochondrial dynamic fusion-fission, mitophagy and cytochrome c-dependent apoptosis are involved. In addition, prolonged endoplasmic reticulum stress will result in apoptosis. Rupture of the lysosomal membrane was associated with inflammation, and both induction of autophagy and blockade of autophagic flow can result in cytotoxicity. Finally, the network mechanism of the combined action of multiple organelle dysfunction, apoptosis, autophagy and oxidative stress was discussed.

Graphene oxide and carbon dots as broad-spectrum antimicrobial agents - a minireview

Due to the increasing global population, growing contamination of water and air, and wide spread of infectious diseases, antibiotics are extensively used as a major antibacterial drug. However, many microbes have developed resistance to antibiotics through mutation over time. As an alternative to antibiotics, antimicrobial nanomaterials have attracted great attention due to their advantageous properties and unique mechanisms of action toward microbes. They inhibit bacterial growth and destroy cells through complex mechanisms, making it difficult for bacteria to develop drug resistance, though some health concerns related to biocompatibility remain for practical applications. Among various antibacterial nanomaterials, carbon-based materials, especially graphene oxide (GO) and carbon dots (C-Dots), are promising candidates due to the ease of production and functionalization, high dispersibility in aqueous media, and promising biocompatibility. The antibacterial properties of these nanomaterials can be easily adjusted by surface modification. They are promising materials for future applications against multidrug-resistant bacteria based on their strong capacity in disruption of microbial membranes. Though many studies have reported excellent antibacterial activity of carbon nanomaterials, their impact on the environment and living organisms is of concern due to the accumulatory and cytotoxic effects. In this review, we discuss antimicrobial applications of the functional carbon nanomaterials (GO and C-Dots), their antibacterial mechanisms, factors affecting antibacterial activity, and concerns regarding cytotoxicity.